hide a secret

[angelene001]

Is it correct to say "hide a secret":
It turns out that she isn't a regular, little girl. She hides a secret. It changes all their life.

[bhaisahab]

Is it correct to say "hide a secret":
It turns out that she isn't a regular, little girl. She hides a secret. It changes all their life.

There are several problems with your short text. In the given context it's not possible to say whether the phrase "hides a secret" is OK or not.

[angelene001]

It's a summary of a plot.
John and Sue get married. They adopt a girl. It turns out that she isn't a regular, little girl. She hides a secret. [There's something wrong with her; she's got a demon inside] It changes all their life.

[Raymott]

It's a summary of a plot.
John and Sue get married. They adopt a girl. It turns out that she isn't a regular, little girl. She hides a secret. [There's something wrong with her; she's got a demon inside] It changes all their life.

That's OK as a plot summary. I'd remove the comma in "regular, little girl". "It changes all their lives."

[5jj]

It's a summary of a plot.

It's amazing what a difference a little context can make.